Dipole antenna elements have been disclosed, for example, in the prior publications DE 197 22 742 A and DE 196 27 015 A. The dipole antenna elements may in this case comprise a normal dipole structure or, for example, may comprise a cruciform dipole arrangement or a dipole square, etc. A so-called reflector cruciform dipole is disclosed in the prior publication WO 00/39894. The structure appears to be comparable with a dipole square. Owing to the specific configuration of the dipole antenna element according to this prior publication, however, this results in the end in a cruciform dipole structure such that the antenna element formed in this way can transmit and receive in two mutually perpendicular polarizations. All of these prior publications, as well as the other dipole structures which have been known to an average person skilled in the art for a long time, are to this extent also included in the content of the present application.
The object of the exemplary illustrative non-limiting technology herein is to provide an improved antenna having at least one dipole or an antenna element which is similar to a dipole, which has characteristic electrical characteristic values which are clearly reproducible in comparison to conventional antennas and which, if required, may in this case even be assembled more easily.
While, until now, all generations of dipole antenna elements or of antenna elements which are similar to dipoles have been based on the idea of them being mounted on a reflector plate such that they are electrically conductively connected to it, the exemplary illustrative non-limiting implementation is in contrast based on the idea of an antenna element such as this being capacitively coupled to the reflector plate. With the interposition of a non-conductive element, in particular a dielectric, this means that the antenna element can be positioned in a clearly reproducible manner from the electrical point of view, on the reflector plate, since the intermodulation problems which occur in some circumstances according to the prior art are avoided. This is because, when a dipole or antenna elements which are similar to dipoles is or are mechanically mounted on the reflector plate according to the prior art, it or they have until now normally been fitted on the reflector plate by means of screws or other connecting mechanisms, thus resulting in different contact relationships depending on the assembly accuracy, with the consequence that intermodulation problems could occur, and express themselves in different ways.
In this case, it is also necessary to remember that, in the majority of all situations, the dipoles or antenna elements which are similar to dipoles are fitted on the reflector plate and are attached from the rear face of the reflector by screwing in one or more screws. However, if the contact pressure also decreases, for example as a result of thermal influences, then the contact relationships change, thus significantly detracting from the performance of an antenna element such as this.
A dipole or an antenna element which is similar to a dipole is thus preferably mounted, together with the dipole halves which actually transmit and receive and with its or their balancing device which is preferably integrally connected to it, on an electrically non-conductive cap, which is in turn fixed on the reflector plate.
However, a modified form is also possible, in which a dipole or antenna element which is similar to a dipole and which in either case is electrically conductive overall is used, including an electrically conductive attachment cap, but in which case, in order to avoid any conductive contact with the reflector, no insulating intermediate cap or non-conductive intermediate layer is used and, instead of this, the dipole or the antenna element which is similar to a dipole is, for example, coated or provided, at least in the area of its attachment section located at the bottom, with a plastic layer, that is to say in general an electrically non-conductive surface.
It is thus evident from the above statements that there is no conductive contact between the dipole or the dipole arrangement and the reflector, but that a capacitive coupling is produced by the preferably insulated mounting process. This also results in the advantage that no potential difference can occur between the dipole and the reflector. This is because the differently chosen materials for a dipole antenna element or the balancing device for a dipole antenna element and the material of the reflector mean that an electrochemical voltage is otherwise normally formed, which can lead to contact corrosion. Since the exemplary illustrative non-limiting implementations avoid this, this also results in a greater possible range of choice for the materials to be used for the dipole and/or for the reflector.
Furthermore, according to exemplary illustrative non-limiting implementations, it is also possible to use plastic dipoles which have only partial metallization, that is to say in particular with these plastic dipoles not being metallized in the area in which they make contact with and are connected to the reflector. The balancing device is in this case preferably regarded as being electrically conductive, as part of the dipole arrangement.
Finally, the principle according to exemplary illustrative non-limiting implementations also results in the mechanical and electrical functions being separated. There is now no need for any high contact or surface pressures, since there is no longer any need for a permanent electrical contact connection all the time between the dipole and its balancing device on the reflector.
Finally, an exemplary illustrative non-limiting dipole arrangement may also be plugged directly onto a board mount so that no additional plastic part is required in situations such as these. The feed could in this case be provided directly via the rear face of the board structure, on which the matching structure is provided.
The explained principle in this case applies to all types of dipoles, vertical dipoles, dipoles polarized in an X-shape (that is to say at angles of ±45° to the horizontal) for single-band antennas, dual-band antennas or for dipole structures, in particular square dipole structures, in which two or more antenna elements are arranged within one another and are intended for different frequency bands.
In one preferred exemplary illustrative non-limiting implementation, a suitable stamped-out area is provided in the reflector plate, into which the attachment cap of the antenna element can, for example, be clipped or inserted, and can be rotated etc. to the final fixing position. In this case, locking and attachment elements can be used, for example those known in the form of so-called bayonet fittings, including all the modified forms associated with them.